The invention relates to a solution for the coating of and activation of non-conductive surfaces for subsequent chemical metallization and also for the galvanic reinforcement of this coating, and to a process of metallization using such solutions.
The metallization of, in particular, non-conductive surfaces is known to require a pretreatment, for which several methods have already become known.
Thus, surfaces are treated, after their pickling with chromosulfuric acid, with solutions of palladium chloride, platinum chloride or gold chloride and then with a reducing solution for reducing the precious metal ions to metal.
According to another method, colloidal precious metal solutions are used, which already catalyze the surfaces without subsequent reduction.
On the surfaces catalyzed by these methods, it is then possible to deposit without the use of current, adhesive metal coatings by further treatment with metal salt solutions and action of a reducing agent.
These methods of metallization serve predominantly for the production of printed circuits and dielectric supports, and are therefore of great importance in the electrical industry.
A disadvantage of the known methods, however, for example, consists in that, when using palladium chloride as previous metal salt and tin-II chloride as reducing agent separately, only the activation of so-called non-coated, i.e. copper-metal free, support material is possible, for otherwise the precious metal would precipitate from the solution.
Activating solutions containing both the precious metal salt and the reducing agent, on the other hand, involve the disadvantage of a special sensitivity to impurity ions and other impurities, resulting in an irreversible coagulation of the precious metal.